1
JEE Main 2021 (Online) 27th August Morning Shift
MCQ (Single Correct Answer)
+4
-1
In a photoelectric experiment, increasing the intensity of incident light :
A
increases the number of photons incident and also increases the K.E. of the ejected electrons
B
increases the frequency of photons incident and increases the K.E. of the ejected electrons
C
increases the frequency of photons incident and the K.E. of the ejected electrons remains unchanged
D
increases the number of photons incident and the K.E. of the ejected electrons remains unchanged
2
JEE Main 2021 (Online) 26th August Evening Shift
MCQ (Single Correct Answer)
+4
-1
The de-Broglie wavelength of a particle having kinetic energy E is $$\lambda$$. How much extra energy must be given to this particle so that the de-Broglie wavelength reduces to 75% of the initial value?
A
$${1 \over 9}$$E
B
$${7 \over 9}$$E
C
E
D
$${16 \over 9}$$E
3
JEE Main 2021 (Online) 26th August Morning Shift
MCQ (Single Correct Answer)
+4
-1
In a photoelectric experiment ultraviolet light of wavelength 280 nm is used with lithium cathode having work function $$\phi$$ = 2.5 eV. If the wavelength of incident light is switched to 400 nm, find out the change in the stopping potential. (h = 6.63 $$\times$$ 10$$-$$34 Js, c = 3 $$\times$$ 108 ms$$-$$1)
A
1.3 V
B
1.1 V
C
1.9 V
D
0.6 V
4
JEE Main 2021 (Online) 27th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
If 'f' denotes the ratio of the number of nuclei decayed (Nd) to the number of nuclei at t = 0 (N0) then for a collection of radioactive nuclei, the rate of change of 'f' with respect to time is given as :

[$$\lambda$$ is the radioactive decay constant]
A
$$-$$ $$\lambda$$ (1 $$-$$ e$$-$$$$\lambda$$t)
B
$$\lambda$$ (1 $$-$$ e$$-$$$$\lambda$$t)
C
$$\lambda$$e$$-$$$$\lambda$$t
D
$$-$$ $$\lambda$$e$$-$$$$\lambda$$t
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